The cycle of revisions I've been working on in the last year and a half or so is winding down to a fixed set of features that I really like. But I have found there's one thing I've had a hard time giving up: case marking. A hefty chunk of what I'm aiming for is inspired by various areal features of North American native languages, where case marking (and dependency marking in general) is not exactly common.
Removing cases gives me deep anxieties, even though I know intellectually a language is perfectly capable of working fine without them, even if you have a nonconfigurational syntax. I spent part of today working through the behavior of applicatives, and have finally reassured myself multiple objects without overt marking can work just fine. Thinking about reasonable discourse situations, rather than concocted grammar puzzles of the sort one finds in old Latin textbooks, is a better guide to where real ambiguities can arise.